Cobalt-containing solutions, such as sludges and leach solutions from cemented carbide or tungsten recovery operations, may be processed to recover cobalt metal powder. It is desirable to remove from the resulting cobalt metal powder any impurities, such as calcium, magnesium and/or silicon, which may adversely affect the performance of cobalt when it is used as a binder in cemented carbides.
U.S. Pat. Nos. 4,214,895 to Gingerich et al., 4,690,710 to Scheithauer et al., and 4,612,039 to Scheithauer et al. describe methods for producing pure cobalt metal powder. U.S. Pat. No. 4,218,240 to Gingerich et al. describes a method for making hexammine cobaltic compounds and a method for making pure cobalt metal powder therefrom.